EP2600513A1 - Stromversorgung für LED-Lichtquellen - Google Patents

Stromversorgung für LED-Lichtquellen Download PDF

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Publication number
EP2600513A1
EP2600513A1 EP11191357.0A EP11191357A EP2600513A1 EP 2600513 A1 EP2600513 A1 EP 2600513A1 EP 11191357 A EP11191357 A EP 11191357A EP 2600513 A1 EP2600513 A1 EP 2600513A1
Authority
EP
European Patent Office
Prior art keywords
power supply
control unit
switches
led light
light source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11191357.0A
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English (en)
French (fr)
Inventor
Michal Soldan
Mário Skalický
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vossloh Schwabe Lighting Solutions GmbH and Co KG
Original Assignee
Vossloh Schwabe Lighting Solutions GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vossloh Schwabe Lighting Solutions GmbH and Co KG filed Critical Vossloh Schwabe Lighting Solutions GmbH and Co KG
Priority to EP11191357.0A priority Critical patent/EP2600513A1/de
Publication of EP2600513A1 publication Critical patent/EP2600513A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
    • H02M3/1586—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel switched with a phase shift, i.e. interleaved

Definitions

  • the invention relates to a power supply for an LED light source.
  • LED light sources are increasingly used for lighting applications where they may replace incandescent lamps and even fluorescent lamps or other discharge lamps. It is known that LEDs must not be directly connected to the electrical grid. Neither can be used ballasts designed for driving fluorescent lamps. Many attempts have been made to design power supplies specifically adapted to power LEDs.
  • WO 2004/057924 A1 discloses an LED power supply including a power converter with an isolating transformer.
  • the primary winding of the transformer is connected to a controlled switch intermittently supplying current to the primary winding.
  • a first secondary winding and the primary winding together form a flyback transformer which supplies power to the LEDs via a rectifier diode each time the switch opens.
  • a second secondary winding in cooperation with the primary winding form a forward converter for charging a capacitor and providing a reference signal across a Zener diode. Further circuits are provided for controlling the voltage across the LED light source and/or the current flowing therethrough.
  • a primary object of the invention is to provide a power supply, in particular a high-power supply, for an LED light source being reliable and efficient.
  • the inventive power supply comprises at least two flyback converters both comprising a switch, a transformer and a rectifier diode.
  • the two converters are controlled by a control unit which controls the two flyback converters so that they power the LEDs in combination.
  • the total LED current is a combined current supplied by the two converters.
  • the peak currents of the two converters are considerably smaller than the peak current of one single converter operating at the same switching frequency and supplying the same average current. Consequently, the RMS value of the supplied current of the inventive power supply is smaller than the RMS current of a single converter power supply.
  • the inventive power supply can be designed for relatively high power ratings just by using at least two flyback converters and adding additional flyback converters if necessary.
  • the flyback converters comprise transformers which comprise isolated primary and secondary windings and provide galvanic isolation of the LEDs form the grid.
  • the transformers comprise independent magnetic armatures which are magnetically decoupled. The magnetic flow of one transformer does not leak to another transformer.
  • the at least two switches of the inventive power supply are operated with one single fixed frequency.
  • the switches are preferably driven in a fixed phase relationship. Preferably a 180° phase relationship is used. It is possible, however, to use different timings, phases and switching schemes if desired.
  • PWM modulate the switching frequency of at least one of the switches This can be done for controlling the voltage across the LEDs, the current through the LEDs or the power supplied to the LEDs. In the course of the PWM modulation the duty cycle of the switching signal may be modified. This can be done to both switches in the same way. However, it is also possible to totally switch off one of the two flyback converters if desired while continuously operating the other. This can be used for achieving very deep dimming levels and to reduce the power losses under those conditions.
  • control unit may basically define equal duty cycles for both switches. However, it is possible to have the control unit define different duty cycles for the two switches. It may be useful for example to watch the temperature of the switches and to reduce the duty cycle of the hotter switch if the two switches have different temperatures. It is possible to balance the operating temperatures of the two switches that way.
  • Figure 1 discloses a power supply 10 for an LED light source 11 consisting of at least one LED 12. Further LEDs 13 through 16 may be connected in series to LED 12. The number of LEDs may vary form embodiment to embodiment as may the colour and rated power. Moreover, further devices may be connected in parallel or in series to the illustrated LEDs.
  • LED refers primarily to light emitting diodes and shall cover any semi-conductor based light source including organic LEDs.
  • the power supply 10 receives electrical energy from an electrical grid 17 and supplies LED current i LED to the LED light source 11. While the electrical grid provides an alternating voltage between 100 V and 300 V (e.g. 230 V) at a frequency of 50 Hz or 60 Hz the LED current i LED is mainly a direct current (DC). Preferably, the strength and waveform of the current will be controlled by the power supply 10.
  • the power supply 10 comprises a rectifier unit 18 transforming the AC voltage of grid 17 into a DC voltage with high crest.
  • the voltage periodically varies from zero to peak voltage with a frequency double of the grid frequency.
  • Two flyback converters 19 and 20 are connected in parallel between primary ground line 21 and supply line 22.
  • Supply line 22 is connected to the positive output of rectifier 18 while primary ground line 21 is connected to the negative output of rectifier 18.
  • the two flyback converters 19 and 20 have outputs 23, 24 connected in parallel to a buffer capacitor 25 located on the secondary side for smoothening the output voltage and supplying DC current i LED to the LED light source 11.
  • the first flyback converter 19 comprises a controllable switch S1, which may be any type of electronically controllable switches.
  • switch S1 is a transistor of any suitable type e.g. a MOSFET, an IGBT, a Junction FET or the like.
  • the control electrode (gate electrode) 26 is connected to a control unit 27 that gives control signals to the switch S1 for opening and closing a flow path between electrodes 28 and 29 (source and drain).
  • a shunt resistor 30 may be provided for sensing the current flowing through switch S1.
  • Shunt resistor 30 is connected to the ground line 21 with one electrode thereof and to switch S1 at the other electrode thereof.
  • the voltage dropping across shunt resistor 30 may be supplied to control unit 27.
  • a primary winding LP1 of a transformer 31 is connected to line 22 at one end thereof and to switch S1 at the other end.
  • the transformer 31 comprises a secondary winding LS1 which is connected to the secondary ground line 42 at one end thereof and to a rectifier diode 32 at the other end thereof.
  • Rectifier diode 32 in turn is connected to the buffer capacitor 25.
  • Phase dots at windings LP1 and LS1 indicate the orientation of windings LP1 and LS1 relative to one another in figure 1 .
  • Flyback converter 20 may have basically the same structure.
  • a second switch S2 is provided having a gating electrode 33, which also is connected to control unit 27. Further electrodes 34, 35 are connected to the primary winding LP2 of a second transformer 36 and to a shunt resistor 37, respectively.
  • second transformer 36 comprises a second secondary winding LS2 which is connected to a second rectifier diode 38 which has the same polarity as does the first rectifier diode 32 and which is also connected to the buffer capacitor 25 for charging.
  • the two flyback converters 19 and 20 may comprise further devices. Figure 1 and the description are restricted to main components of the converters, however. It should be well understood that the two flyback converters 19 and 20 may have the same structure, devices, and rated power if desired. However, it is possible to differently design the two flyback converters 19 and 20, if appropriate. This may be useful if a wide dimming range is desired. In those cases full power is obtained by running both flyback converters 19 and 20 and the deepest dimming level is reached by running only the smaller converter of the flyback converters 19 and 20 with reduced power. Further it is to be understood that one or some more flyback converters may be connected in parallel to the two flyback converters 19 and 20 if desired.
  • capacitor 25 may be any type of capacitor. It may be one single device or a combination of different capacitors, filters or the like.
  • transformers 31 and 36 have separate cores and preferably do not magnetically couple one to another. It is to be understood that the transformers 31, 36 may have further windings, e.g. windings which may be connected to control unit 27. Those control windings may be used for controlling the flyback converters 19 and 20.
  • Control unit 27 may be connected to a measuring unit 39, which is connected to the LED light source 11.
  • a shunt resistor 40 may be connected in series to LED source 11.
  • the measuring unit 39 senses the voltage drop over the LED light source 11 and the voltage drop on shunt resistor 40 for acquiring data indicating the voltage across and/or the current i LED through the LED light source 11.
  • Signals characterizing the voltage drop across LED light source 11 and/or LED current i LED may be sent via channel 41 to the control unit 27.
  • the channel 41 may comprise one or several lines as appropriate.
  • flyback converters 19 and 20 preferably are operated in an interleaved order.
  • the first switch S1 and the second switch S2 alternately open and close.
  • Figure 2 provides the timing of the currents resulting therefrom.
  • the left part of Figure 2 shows the current i1 flowing through switch S1 and the current i2 flowing through switch S2. It is assumed that both flyback converters 19 and 20 operate with full power in a slightly overlapping fashion. Shortly after i1 starts rising (switch S1 is closed) the current i2 flowing through switch S2 peaks. At the time t1 switch S2 opens while switch S1 remains closed. Opening switch S2 interrupts current i2 so that it drops to 0. However, the current commutes to the secondary winding LS2.
  • the resulting current iS2 de-charges the second transformer 36 and charges the capacitor 25.
  • the de-charging current iS2 will reach 0 within short. Once it reached 0 at a point of time t2 or shortly thereafter at a point of time t3 switch S2 may again be closed. The current i2 may rise again. Meanwhile or shortly afterwards switch S1 may open and interrupt the primary current i1. This generates the secondary current iS1 of the first flyback converter 19, which de-charges the first transformer 31 and charges the capacitor 25.
  • the two charging currents i1 and i2 combine into an input current ii which may be well above 0 and has a rather low ripple.
  • the peak values are not much above the average value marked by a dotted line in Figure 2 . Consequently, the losses depending on the root mean square (RMS) value of the current will be restricted to low numbers.
  • RMS root mean square
  • the control unit 27 may control the power of the two flyback converters 19 and 20 by pulse width modulating (PWM) the control signals controlling the switches S1 and S2.
  • PWM pulse width modulating
  • the right part of Figure 2 illustrates the operation of the two flyback converters 19 and 20 with reduced duty cycles. While the switches S1 and S2 are switched on for more than 50% of one cycle at the left hand side of Figure 2 they are switched on for less than 50% of one cycle in the right part of Figure 2 . It is seen that still both flyback converters 19 and 20 have the same or at least similar duty cycles. However, it is noted that it is also possible to operate the two flyback converters 19 and 209 with different duty cycles.
  • the measurement unit 39 may primarily be a current sensor sensing the LED current i LED . It may be desired to keep this current constant under most working conditions. If so, measuring unit 39 sends signals to control unit 27 for varying the duty cycles of the two flyback converters 19 and 20 to match the LED current i LED to the desired current.
  • the measuring unit 39 measures a value which indicates the current i LED supplied to the LED light source 11.
  • the signal supplied via channel 41 to control unit 27 may be compared by the control unit 27 with a reference value. The control unit 27 will produce an error value indicating any mismatch between the reference value and the sensed value of the LED current i LED .
  • control unit 27 may vary just the duty cycle of one of the converters 19 and 20.
  • the inventive power supply 10 for an LED light source 11 comprises two flyback converters 19 and 20 which are connected in parallel and which are controlled by a single control unit 27.
  • a measuring unit 39 may be provided which acquires at least one of the voltage drop across the LED light source 11, the current flowing through the LED light source 11, or the power supplied to the LED light source 11.
  • the two flyback converters 19 and 20 are preferably operating in interleaved fashion so that the two switches S1 and S2 alternately open and close. Nonetheless, the control unit may define duty cycles different from 50% so that periods may exist in which both switches S1 and S2 are closed and/or periods in which both switches S1 and S2 are open.
EP11191357.0A 2011-11-30 2011-11-30 Stromversorgung für LED-Lichtquellen Withdrawn EP2600513A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP11191357.0A EP2600513A1 (de) 2011-11-30 2011-11-30 Stromversorgung für LED-Lichtquellen

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP11191357.0A EP2600513A1 (de) 2011-11-30 2011-11-30 Stromversorgung für LED-Lichtquellen

Publications (1)

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EP2600513A1 true EP2600513A1 (de) 2013-06-05

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3739741A1 (de) * 2019-05-15 2020-11-18 Goodrich Corporation Verschachtelter boost-wandler mit kapazitivem multiplizierer für led-ansteuerung

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030048648A1 (en) * 2001-09-13 2003-03-13 Feng Lin Current sense and control of DC/DC converters
WO2004057924A1 (en) 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Leds driver
US20090257257A1 (en) * 2008-04-10 2009-10-15 Stmicroelectronics S.R.I. Control device for interleaved converters, a system of interleaved converters and related control method
US20090267658A1 (en) * 2008-04-29 2009-10-29 Bridge Christopher D Synchronizing Frequency and Phase of Multiple Variable Frequency Power Converters

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030048648A1 (en) * 2001-09-13 2003-03-13 Feng Lin Current sense and control of DC/DC converters
WO2004057924A1 (en) 2002-12-19 2004-07-08 Koninklijke Philips Electronics N.V. Leds driver
US20090257257A1 (en) * 2008-04-10 2009-10-15 Stmicroelectronics S.R.I. Control device for interleaved converters, a system of interleaved converters and related control method
US20090267658A1 (en) * 2008-04-29 2009-10-29 Bridge Christopher D Synchronizing Frequency and Phase of Multiple Variable Frequency Power Converters

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3739741A1 (de) * 2019-05-15 2020-11-18 Goodrich Corporation Verschachtelter boost-wandler mit kapazitivem multiplizierer für led-ansteuerung
US11109460B2 (en) 2019-05-15 2021-08-31 Goodrich Corporation Interleaved boost converter with capacitive multiplier for LED drive

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